[스프링 데이터 JPA] JPA 프로그래밍 7: Query

JPQL (HQL)

• Java Persistence Query Language / Hibernate Query Language
• 데이터베이스 테이블이 아닌, 엔티티 객체 모델 기반으로 쿼리 작성
• JPA 또는 하이버네이트가 해당 쿼리를 SQL로 변환해서 실행함
• https://docs.jboss.org/hibernate/orm/5.2/userguide/html_single/Hibernate_User_Guide.html#hql

Hibernate ORM 5.2.18.Final User Guide

Criteria

https://docs.jboss.org/hibernate/orm/5.2/userguide/html_single/Hibernate_User_Guide.html#criteria

Hibernate ORM 5.2.18.Final User Guide

 

Native Query

https://docs.jboss.org/hibernate/orm/5.2/userguide/html_single/Hibernate_User_Guide.html#sql

Hibernate ORM 5.2.18.Final User Guide

 

QueryRunner를 통한 테스트

@Component
@Transactional
public class QueryRunner implements ApplicationRunner {

    @PersistenceContext
    EntityManager entityManager; 

    @Override
    public void run(ApplicationArguments args) throws Exception {
        /**
         * JPQL - 타입세이프 X
         */
        TypedQuery<Post> query = entityManager.createQuery("SELECT p FROM Post AS p", Post.class);	// Post는 엔티티 이름이다.
        List<Post> jpqlResultList = query.getResultList();
        jpqlResultList.forEach(p -> System.out.println(p.toString()));

        /**
         * Criteria - 타입세이프 O
         * */
        CriteriaBuilder builder = entityManager.getCriteriaBuilder();
        CriteriaQuery<Post> criteriaQuery = builder.createQuery(Post.class);
        Root<Post> from = criteriaQuery.from(Post.class);
        criteriaQuery.select(from);

        List<Post> criteriaResultList = entityManager.createQuery(criteriaQuery).getResultList();
        criteriaResultList.forEach(p -> System.out.println(p.toString()));

        /**
         * Native Query
         * */
        List<Post> nativeQueryResultList = entityManager.createNativeQuery("SELECT * FROM POST", Post.class).getResultList();
        nativeQueryResultList.forEach(p -> System.out.println(p.toString()));

    }
}